1. Field of the Invention
The present invention relates to a rotary atomizing electrostatic coating apparatus having a plurality of paint feed nozzles per rotary atomizing head, called multi-feed nozzle-type coating apparatus.
2. Description of Related Art
Japanese Patent Publication No. HEI 6-134354 disclosed a multi-feed, nozzle-type rotary atomizing electrostatic coating apparatus.
In the apparatus, as illustrated in FIGS. 6 and 7, a paint feed nozzle assembly 21 for feeding paint to a rotary atomizing head 25 is disposed within a thinner feed nozzle 24. The nozzle assembly 21 includes a center nozzle 22 disposed on an axis of rotation of the rotary atomizing head 25 and a plurality of surrounding nozzles 23 arranged around the center nozzle 22. The rotary atomizing head 25 includes a central portion (or hub) having a self-cleaning bore 26 for letting thinner from the thinner nozzle 24 pass therethrough to self-clean a front surface of the atomizing head 25.
When a color of a current paint is changed, feeding the current color paint from a current paint feed nozzle is stopped, then thinner is fed through the thinner tube 24 to clean the atomizing head 25. After cleaning is completed, feeding of the thinner is stopped, and then feeding paint of another color through another paint feed nozzle is started.
However, in the conventional apparatus, because a paint injection pattern from the surrounding paint nozzles 23 interferes with the self-cleaning bore 26, the paint expelled from the surrounding nozzles 23 at a high speed during metallic top coating enters the self-cleaning bore 26 at a high speed and passes through the self-cleaning bore 26. Because a centrifugal force does not act on the passing paint, the passing paint flows straight ahead to collide with a workpiece to be coated and causes a coating problem.